SSL Certificates

X.509 is an ITU standard defining the format of public key certificates. X.509 are used in TLS/SSL, which is the basis for HTTPS. An X.509 certificate binds an identity to a public key using a digital signature. A certificate contains an identity (hostname, organization, etc.) and a public key (RSA, DSA, ECDSA, ed25519, etc.), and is either signed by a Certificate Authority or is Self-Signed.

Self-Signed Certificates

Generate CA

Generate RSA

openssl genrsa -aes256 -out ca-key.pem 4096

Generate a public CA Cert

openssl req -new -x509 -sha256 -days 365 -key ca-key.pem -out ca.pem

Generate Certificate

Create a RSA key
```
openssl genrsa -out cert-key.pem 4096
```

Create a Certificate Signing Request (CSR)

openssl req -new -sha256 -subj "/CN=yourcn" -key cert-key.pem -out cert.csr

Create a extfile with all the alternative names

echo "subjectAltName=DNS:your-dns.record,IP:257.10.10.1" >> extfile.cnf

# optional
echo extendedKeyUsage = serverAuth >> extfile.cnf

Create the certificate

openssl x509 -req -sha256 -days 365 -in cert.csr -CA ca.pem -CAkey ca-key.pem -out cert.pem -extfile extfile.cnf -CAcreateserial

Certificate Formats

X.509 Certificates exist in Base64 Formats PEM (.pem, .crt, .ca-bundle), PKCS#7 (.p7b, p7s) and Binary Formats DER (.der, .cer), PKCS#12 (.pfx, p12).

Convert Certs

COMMAND	CONVERSION
`openssl x509 -outform der -in cert.pem -out cert.der`	PEM to DER
`openssl x509 -inform der -in cert.der -out cert.pem`	DER to PEM
`openssl pkcs12 -in cert.pfx -out cert.pem -nodes`	PFX to PEM

Verify Certificates

openssl verify -CAfile ca.pem -verbose cert.pem

Install the CA Cert as a trusted root CA

On Debian & Derivatives

Move the CA certificate (ca.pem) into /usr/local/share/ca-certificates/ca.crt.
Update the Cert Store with:
```
sudo update-ca-certificates
```

Refer the documentation here and here.

On Fedora

Move the CA certificate (ca.pem) to /etc/pki/ca-trust/source/anchors/ca.pem or /usr/share/pki/ca-trust-source/anchors/ca.pem
Now run (with sudo if necessary):
```
update-ca-trust
```

Refer the documentation here.

On Arch

System-wide – Arch(p11-kit) (From arch wiki) - Run (As root)

trust anchor --store myCA.crt

- The certificate will be written to /etc/ca-certificates/trust-source/myCA.p11-kit and the "legacy" directories automatically updated. - If you get "no configured writable location" or a similar error, import the CA manually: - Copy the certificate to the /etc/ca-certificates/trust-source/anchors directory. - and then

update-ca-trust

wiki page here

On Windows

Assuming the path to your generated CA certificate as C:\ca.pem, run:

Import-Certificate -FilePath "C:\ca.pem" -CertStoreLocation Cert:\LocalMachine\Root

- Set -CertStoreLocation to Cert:\CurrentUser\Root in case you want to trust certificates only for the logged in user.

OR

In Command Prompt, run:

certutil.exe -addstore root C:\ca.pem

certutil.exe is a built-in tool (classic System32 one) and adds a system-wide trust anchor.

On Android

The exact steps vary device-to-device, but here is a generalised guide: 1. Open Phone Settings 2. Locate Encryption and Credentials section. It is generally found under Settings > Security > Encryption and Credentials 3. Choose Install a certificate 4. Choose CA Certificate 5. Locate the certificate file ca.pem on your SD Card/Internal Storage using the file manager. 6. Select to load it. 7. Done!

SSL Security Cheat-Sheet

... TBD

TLS Version and Ciphers

Scanning for TLS Version and supported Ciphers: nmap --script ssl-enum-ciphers <target>

Tool	Link	Description
Qualys SSL Labs	https://www.ssllabs.com/projects/index.html	SSL Security Tools by Qualys